1. Field of the Invention
The present invention relates generally to chucks and, more particularly, to an equalizing chuck.
2. Description of the Related Art
Work holding chucks having a plurality of radially shiftable segments that act to operate a plurality of work holding jaws through rocker arms are known as disclosed in U.S. Pat. No. 3,365,206. Such chucks are typically used for fragile or thin walled parts or for compensating for issues of roundness. These chucks may include a plurality of wedge-shaped members positioned within the body of the chuck and engaging lower sections of the rocker arms. A flexible band or spring surrounds the wedge-shaped members. An actuator is secured within the chuck for axial travel. Axial travel of the actuator causes outward movement of the wedge-shaped members which correspondingly drive the lower sections of the rocker arms outward causing the rocker arms to pivot and urge the jaws inward.
If the jaws simultaneously grip the workpiece, the wedge-shaped members engaging the actuator are not displaced and the gripping force applied by each set of jaws is relatively constant. If one pair of opposite jaws engage the workpiece first, the corresponding wedge member then begins to slide inward. As the wedge member slides inward, it drives an adjacent wedge outward, thus increasing the distance the adjacent jaw travels. As discussed, the wedges are held in position by the flexible band which distorts when the wedges move. However, the use of such a spring or flexible band decreases the sensitivity of the equalizing chuck. For instance, the wedges must overcome the spring force in order to equalize. Furthermore, the band must be of sufficient strength to overcome any centrifugal force during operation of the chuck. It is recognized that the centrifugal force would act to throw the wedges outward, thus increasing the clamping force and possibly damaging the workpiece.